Hybrid Simulation for Electrically Large Antenna Platforms

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Hybrid Simulation for Electrically Large Antenna Platforms Jim Creed 2016-04-12

CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com

Outline

Introduction to hybrid simulation

Selected antenna platform examples

Conclusions


The problem…

1.6 GHz

4.5 m

24 λ

1.1 GHz

160 m

560 λ

features:

1 mm

features:

0.5 mm


CST MWS solver choice

A Range of Solvers…

Ray Tracing

Volumetric Mesh Surface Mesh

Full Wave

Time Domain

FIT, TLM Hexahedral Mesh Conformal (PBA)

Frequency Domain

FEM Tetrahedral Mesh

Curved

Integral Equation

MOM, MLFMM Surface Mesh

Curved

Asymptotic Solver

SBR Surface Mesh

Curved


…for a Range of Applications


Platform Electrical Size

El. Length

1λ

10λ

100λ

1000λ

10000λ

MoM MLFMM


1. Installed Antenna Scenario

2 GHz

17.4 x 4.5 x 16.2 m

116 x 30 x 108 λ

375,840 λ3

2 GHz blade antenna positioned on aircraft

660 million cells


1. "Brute Force" Simulation

Single workstation with 2 Kx80

Total memory: < 100 GB

Broadband calculation time ~ few hours

660 million cells

2 GHz blade antenna positioned on aircraft

2 GHz

17.4 x 4.5 x 16.2 m

116 x 30 x 108 λ

375,840 λ3


2. What if the challenge increases?

aircraft length = 42.6 m

(>2000 λ @ 14.5 GHz)

array(s): 100s of elements element: fine geometry

via radius = 0.4 mm

Several hundred billion cells

Impossible to simulate using only one solver!


Hybrid: SMALL BIG

near field source

(equivalence principle)

farfield source


CST MWS Solver ̎ Coupling ̎

1. Combination of different solvers. Coupling

via field

interfaces

2. Loop over the same solver.


Antenna

choice/synthesis

Of interest:

Antenna Specifications Operating frequency

Farfield

…

Suitable topologies

Antenna

placement

Of interest:

Installed farfield

Coupling with other

antennas

Nearfield calculation

Antenna Placement Workflow

Antenna

simulation

Of interest:

Integration with

other antennas

Matching circuit

Radome


Antenna

choice/synthesis

Antenna

placement

Antenna Placement Workflow

Antenna

simulation

Different tool/solvers available at each stage…


Outline


Selected antenna platform examples

Conclusions


Three Installed Antenna Examples

1. UAV

2. Satellite

3. Aircraft


a) Antenna placement @ lower frequencies

+ Simple antenna topologies (easy to build from scratch).

+ EM problem not electrically large.

b) Antenna placement @ higher frequencies

More complex antenna topologies (more difficult to build

from scratch).

EM problem electrically large.

UAV Possible Scenarios


a) Lower Frequencies

VHF blade

30-100 MHz

IFF1 monopole

1020-1100 MHz

IFF2 monopole

1020-1100 MHz

Excitation: Lumped ports @ 50 Ohm


Brodband Analysis using FIT Calculation time ~ 7min

E-Field @ 1.06 GHz (IFF1)

Farfield @ 1.06 GHz (IFF1)

Polar plot with

structure overlay


Solution 1 (extract representative antennas)

Solution 2 Use antenna measured data (i.e from MVG).

b) Higher Frequencies

Antenna specification Frequency [GHz]

1 TACAN 1.08

2 GPS 1.575

3 Communication 1.8

4 SATCOM (UHF) 2.3

Antennas from 3rd party CAD of the antennas not available!

placement


A lot of predefined "Aeronautical" antenna specifications.

Specifications can be used to look for suitable antenna topologies

inside Antenna Magus database.

Specification Library


SATCOM Antenna Topologies


4 Parametric Antenna Models + UAV 1 TACAN

2 GPS

3 Communication

(1.8 GHz)

4 SATCOM (UHF)

placement

Extra requirements:

Keep geometrical parameters of each single

project.

Place the antennas on predefined

(parametric) positions.


Schematic

3D Layout

System Assembly and Modelling

3D Layout (aligned antennas using anchor points)


Setup of Simulation Projects

Brute force approach

Field decomposition approach

MLFMM


Installed Antennas using SAM FSC

2. Source(s)

1. Platform

(including part of the platform)


Installed antennas on UAV

4 Sources

Platform

Field sources installed on platform


Curved Tri+Quad Meshing

Quad Less memory

Curved Higher accuracy

Surface based meshing


Available outputs

Broadband antenna to antenna coupling

GPS (fs3) SATCOM (fs4)

E-Field @ 2.3 GHz (SATCOM)

E-Field @ 1.575 GHz (GPS)


Installed farfield @ 1.8 GHz


Three Installed Antenna examples

1. UAV

2. Satellite

3. Aircraft


Design Issues Simulation Issues

source: NASA

Coexistence of

multiple antennas

Thermal / Mechanical

issues

Electromagnetic

design

Installed

performance


Construction of Model

anchor

points

Schematic

3D Layout


Ku band offset Gregorian reflector (14.6 GHz)

Reflector Installed Performance

filtered to show rays with only 3 reflections

ray visualisation directivity

11 m “wingspan”

535 λ @ 14.6 GHz


Three Installed Antenna Examples

1. UAV

2. Satellite

3. Aircraft


Example: Airborne SATCOM

"Earth gravity" by NASA/JPL/University of Texas Center for Space Research. -

http://www.jpl.nasa.gov/news/news.cfm?release=2007-147. Licensed under Public Domain via Commons -

https://commons.wikimedia.org/wiki/F ile:Earth_gravity.png#/media/F ile:Earth_gravity.png

Ku-band SATCOM: linear polarization

Uplink: 14.0 – 14.5 GHz

Downlink: 12.25 – 12.75 GHz

Additional antenna constraints: form factor, mechanical stability,

aerodynamics, weight

Required:

beam steering and

polarization tracking


Installed Performance of Phased Array

Glass modeled using ̎̎ Thin panel ̎̎ material


Outline


Selected aerospace examples

Conclusions


Decomposition of a big volume into subvolumes : SMALLER (Source) fine features can be accurately simulated (e.g details of radiating source)

SIMPLIFIED (Platform) mesh can be relaxed for the full model containing the imported source (e.g. increase

time step, speed-up method convergence).

Simulate source with appropriate mesh and solver.

Import external (measured) fields.

No knowledge of antenna structure necessary (IP).

Advantages of Hybrid Approach


Antenna synthesis

Summary Antenna /Array design

Antenna Installed performance

All antenna design stages with the

best solver in one User Interface

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Hybrid Simulation for Electrically Large Antenna Platforms Jim Creed 2016-04-12

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Hybrid Simulation for Electrically Large Antenna Platforms

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